Method of making a concrete block

ABSTRACT

Molds and processes that permit high-speed, mass production of retaining wall blocks having patterned or other processed front faces, as well as retaining wall blocks formed by such processes. The invention permits the front face of the block to be impressed with a pattern or otherwise directly processed, to allow the formation of pre-determined block front faces, while at the same time facilitating high-speed, high-volume production of blocks. A mirror image of the desired pattern can be created on a stripper shoe by selecting a desired three-dimensional surface from a naturally occurring or man made object and digitally scanning the selected three-dimensional pattern to create scanned data. The scanned data can then be used to machine a face of the stripper shoe that is the mirror image of the selected pattern.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/972,492, filed Aug. 21, 2013, issued as U.S. Pat. No. 8,865,039,which is a continuation of U.S. patent application Ser. No. 13/360,235,filed Jan. 27, 2012, issued as U.S. Pat. No. 8,540,915, which is acontinuation of U.S. patent application Ser. No. 12/639,732, filed Dec.16, 2009, issued as U.S. Pat. No. 8,128,851, which is a continuation ofU.S. patent application Ser. No. 11/697,067, filed Apr. 5, 2007, issuedas U.S. Pat. No. 7,807,083, which is a continuation of U.S. patentapplication Ser. No. 10/359,525, filed Feb. 5, 2003, issued as U.S. Pat.No. 7,208,112, which is a continuation-in-part of U.S. patentapplication Ser. No. 10/038,639, filed Jan. 4, 2002, issued as U.S. Pat.No. 7,140,867, which applications are incorporated herein by referencein their entirety.

FIELD OF THE INVENTION

The invention relates generally to concrete blocks and the manufacturethereof. More specifically, the invention relates to concrete blockssuitable for use in landscaping applications, such as retaining walls,and manufacturing processes useful in the production of such blocks.

BACKGROUND OF THE INVENTION

Modern, high speed, automated concrete block plants and concrete paverplants make use of molds that are open at the top and bottom. Thesemolds are mounted in machines which cyclically station a pallet belowthe mold to close the bottom of the mold, deliver dry cast concrete intothe mold through the open top of the mold, densify and compact theconcrete by a combination of vibration and pressure, and strip the moldby a relative vertical movement of the mold and the pallet.

Due to the nature of such plants and the equipment used to perform thisprocess, it is difficult to impart a natural appearance to the face of aconcrete block, particularly if the block needs to include otherfeatures, such as converging side walls, and an integral locator andshear flange(s) formed on the top and/or bottom face of the block. U.S.Pat. No. 5,827,015, which is incorporated herein by reference, disclosessuch a concrete block suitable for use as a retaining wall block, andthe common method for producing such a block in a high speed, automatedconcrete block plant.

There is demand for a pre-formed concrete unit, particularly a retainingwall block with converging side walls and/or an integral locator andshear flange formed on the top and/or bottom face, and having a morenatural appearing face than is achievable by the splitting processdescribed in U.S. Pat. No. 5,827,015, or by the splitting processdescribed in U.S. Pat. No. 6,321,740, which is also incorporated hereinby reference. In particular, there is a demand for processes and toolingthat will create such blocks with such faces in high-speed, automatedfashion on the type of equipment commonly available in a concrete blockor concrete paver plant.

SUMMARY OF THE INVENTION

The invention relates to molds and processes that permit high speed,mass production of concrete units, and, in particular, retaining wallblocks. These molds and processes can be used to create relativelysimple decorative front faces on such blocks, similar to the split facesdescribed in U.S. Pat. No. 5,827,015. These molds and processes can alsobe used to create more complex front faces on such blocks, similar tothe split and distressed faces produced by conventional tumbling orhammermill processing, or by the process described in U.S. Pat. No.6,321,740. These molds and processes can also be used to create uniqueblocks that have heretofore not been available: retaining wall blockswith converging side walls and/or integral locator and shear flanges andwith front faces with significantly more complex faces, including faceswith significant detail and relief not heretofore available in dry castconcrete block technology.

In a preferred embodiment, the resulting blocks have patterned frontfaces that simulate natural stone, as well as upper and lower faces, arear face, opposed converging side faces, and a flange extending belowthe lower face. Blocks having this construction, when stacked inmultiple courses with other similarly constructed retaining wall blocks,permits construction of serpentine or curved retaining walls that appearto have been constructed with naturally-occurring, rather than man-made,materials.

One aspect of this invention is that a mold made in accordance with theinvention is arranged so that the portion of the block that will be thefront face when the block is laid is facing the open top of the moldcavity during the molding process. This orientation permits the frontface of the block to be formed by the action of a patterned pressureplate (“stripper shoe”) in a high-speed, concrete block or paver plant.The stripper shoe can be provided with a very simple pattern, amoderately complex pattern, or a highly detailed, three-dimensionalpattern with significant relief, simulating naturally occurring stone.Molding the block in this orientation also makes the block face readilyaccessible for other processing to affect the appearance of the face,including the application of specially-selected aggregate and/or colorpigments to the face.

Another aspect of this invention is that a side wall of the mold has anundercut portion adjacent the open bottom of the mold cavity. Thisundercut portion cooperates with the pallet that is positioned under themold to form a subcavity of the mold. In a preferred embodiment, thissubcavity forms the locator and shear flange on the surface of the blockthat will be the bottom of the block as laid.

Another aspect of this invention is that at least one of the side wallsof the mold is angled from vertical, to form a side wall of the block aslaid that includes a portion that converges toward the opposite sidewall as it gets closer to the rear face of the block. This angled moldside wall is moveable, so that it moves into a first position to permitthe mold to be filled with dry cast concrete and the concrete to becompacted and densified, and moves into a second position to permit thedensified concrete to be stripped from the mold without interferencefrom this mold side wall. In a preferred embodiment, the opposed moldside wall is similarly moveable, so that at least portions of theopposed side walls of the resulting block converge towards each other asthey approach the rear of the block.

These and various other advantages and features of novelty whichcharacterize the invention are pointed out with particularity in theclaims annexed hereto and forming a part hereof. However, for a betterunderstanding of the invention, its advantages and objects obtained byits use, reference should be made to the drawings which form a furtherpart hereof, and to the accompanying description, in which there isdescribed a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a retaining wall block according to thepresent invention, with the block being oriented in the position inwhich it is formed in the mold.

FIG. 2 is a bottom plan view of the retaining wall block of FIG. 1.

FIG. 3 is a side elevation view of the retaining wall block of FIG. 1.

FIG. 3A is a detailed view of the portion of the retaining wall blockcontained within the dashed circle in FIG. 3.

FIG. 4 is a front view of a portion of a retaining wall constructed froma plurality of blocks according to the present invention.

FIG. 5 is a flow chart illustrating the process of forming the block ofthe present invention.

FIG. 6 is a perspective view of a mold assembly having a plurality ofmold cavities for forming a plurality of retaining wall blocks of thepresent invention utilizing the process of the present invention.

FIG. 7 is a top plan view of the mold assembly of FIG. 6.

FIG. 8 is an end view of the mold assembly illustrating one mold cavitywith opposed, converging, pivoted side walls.

FIG. 9 is a schematic representation of the side walls that form theupper and lower block faces, the stripper shoe, and the pallet of themold assembly.

FIGS. 10A, 10B, 10C, 10D, 10E and 10F are digital renditions ofrepresentative patterns on the faces of stripper shoes according to thepresent invention.

FIG. 11 is a perspective view of a representative pattern on the face ofa stripper shoe.

FIG. 12 is a flow chart illustrating the process of forming a strippershoe face of the present invention.

FIG. 13 is a schematic illustration of the temperature control for thestripper shoe.

FIGS. 14A, 14B and 14C are photographs of retaining wall blocksaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Overview

The present invention provides a process for producing a concrete block,as well as a block resulting from the process, and a mold and moldcomponents used to implement the process, in which a pre-determinedthree-dimensional pattern is impressed into the face of the block, andthe front face of the block can be otherwise directly processed orworked so that a pre-determined block front face can be produced in astandard dry cast concrete block or paver machine. Direct processing orworking of the front face includes molding, shaping, patterning,impressing, material layering, combinations thereof, and other processesin which the texture, shape, color, appearance, or physical propertiesof the front face can be directly affected. Further, the process can beimplemented using multiple-cavity molds to permit high-speed,high-volume production of the concrete blocks on standard dry castconcrete block or paver equipment. Moreover, use of the inventiveprocess and equipment eliminates the need for a splitting station,and/or a hammermill station, and/or a tumbling station, and theadditional equipment and processing costs associated with suchadditional processing stations.

The blocks produced by the process of the present invention can have aconfiguration that allows construction of walls, including serpentine orcurved retaining walls, by stacking a plurality of blocks, having thesame or different pre-determined front faces, in multiple courses, withan automatic set-back and shear resistance between courses.

The preferred embodiment will be described in relation to the impressingof a pre-determined, three-dimensional, rock-like pattern into the frontface of a retaining wall block. As a result, the block, and a wall thatis constructed from a plurality of the blocks when stacked into courses,appears to have been constructed with “natural” materials. The processdescribed herein could also be used to construct concrete blocks thatare used in the construction of building walls, as well as for concretebricks, slabs and pavers.

Concrete Block

A concrete block 10 according to the present invention is illustrated inFIGS. 1-3. The block 10 comprises a block body having a front face 12, arear face 14, an upper face 16, a lower face 18, and opposed side faces20, 22. (Note that the terms front, rear, upper, and lower facesreference the orientation of the faces of the block as placed within aretaining wall and do not necessarily reflect the orientation of theblock as it is produced.) The block 10 is formed from a cured, dry cast,no slump concrete. Dry cast, no slump concrete is well known in the artof retaining wall blocks.

The front face 12, as shown in FIGS. 1-3, is provided with apre-determined three-dimensional pattern. The pattern on the front face12 is preferably imparted to the front face during molding of the block10 by the action of a moveable stripper shoe (to be later described)having a pattern that is the mirror image of the front face of theblock. FIGS. 14A-C are photos of blocks according to the presentinvention having patterned front faces.

The pattern that is imparted to the front face 12 can vary dependingupon the desired appearance of the front face. Preferably, the patternsimulates natural stone so that the front face 12 appears to be anatural material, rather than a man-made material. The particular stonepattern that is used will be selected based on what is thought to bevisually pleasing to users of the blocks. By way of example, the face ofthe block can be impressed with a pattern that appears to be a singlestone, such as river rock. Or the block can be impressed with a patternthat appears to be multiple river rocks in a mortared together pattern.Or the block can be impressed with a pattern that simulates a singlepiece of quarry rubble, or multiple pieces of field stone, stacked inlayers. Endless possibilities are available. By providing stripper shoeswith a variety of different patterns, the resulting patterns on theblocks can be varied by changing stripper shoes.

The resulting detail and relief that can be provided on the front faceis greater than that which can be provided on a front face of a blockthat results from conventional splitting techniques, and the tumbling,hammermilling and other distressing techniques previously described. Therelief on the patterned front face 12, measured from the lowest point tothe highest point, is preferably at least 0.5 inches, and morepreferably at least 1.0 inches.

In the preferred embodiment, the front face 12 lies generally inapproximately a single plane between the side faces 20, 22, as opposedto the common, three-faceted and curved faces that are frequently seenin split-face retaining wall blocks, although such multi-faceted andcurved faces can be easily produced with the present invention. As shownin FIG. 3, the front face 12 is provided with a slight rearward slant,i.e. inclined at an angle α from the bottom lower face 18 to the upperface 16. Preferably, α is about 10 degrees. As a result, front and rearfaces 12, 14 are separated by a distance d₁ adjacent the lower face 18and by a distance d₂ adjacent the upper face 16, with d₁ being largerthan d₂. In the preferred embodiment, d₁ is about 7.625 inches and d₂ isabout 6.875 inches. The width d₃ is preferably about 12.0 inches. It isalso contemplated that the front face 12 between the side faces 20, 22can be faceted, curved, or combinations thereof. In these embodiments,the front face would also have a slight rearward slant.

Typically, when retaining wall blocks are stacked into set-back coursesto form a wall, a portion of the upper face of each block in the lowercourse is visible between the front face of each block in the lowercourse and the front face of each block in the adjacent upper course.The visible portions of the upper faces create the appearance of aledge. And, in the case of dry cast concrete blocks, this ledgetypically has an artificial appearance. By providing a rearward inclineangle to the front face 12 of the block 10, the appearance of the ledgecan be reduced or eliminated, thus enhancing the “natural” appearance ofthe resulting wall.

The front face 12 also includes radiused edges 24 a, 24 b at itsjunctures with the side faces. The radiused edges 24 a, 24 b are formedby arcuate flanges provided on the stripper shoe. The radius of theedges 24 a, 24 b is preferably about 0.25 inches. The radiused edges 24a, 24 b shift the contact points between the sides of the block 10 withadjacent blocks in the same course, when a plurality of blocks are laidside-by-side, away from the front face 12, and result in better contactbetween the blocks to prevent soil “leakage” between adjacent blocks. Ifdesired, the top and bottom edges at the junctures between the frontface 12 and the upper and lower faces 16, 18 could also be radiused,similar to the radiused edges 24 a, 24 b, by the provision of arcuateflanges on the stripper shoe.

With reference to FIGS. 1-3, the rear face 14 of the block 10 isillustrated as being generally planar between the side faces 20, 22 andgenerally perpendicular to the upper and lower faces 16, 18. However, itis contemplated that the rear face 14 could deviate from planar, such asby being provided with one or more notches or provided with one or moreconcavities, while still being within the scope of the invention. Thewidth d₄ of the rear face 14 is preferably about 8.202 inches.

Further, the upper face 16 is illustrated in FIGS. 1-3 as beinggenerally planar, and free of cores intersecting the upper face 16. Whena plurality of blocks 10 is stacked into courses to form a wallstructure, the upper face 16 of each block is in a generally parallelrelationship to the upper faces 16 of the other blocks.

The lower face 18 of the block 10 is formed so as to be suitable forengaging the upper face 16 of the block(s) in the course below tomaintain the generally parallel relationship between the upper faces ofthe blocks 10 when the blocks are stacked into courses. In the preferredembodiment, as illustrated in FIGS. 1-3, the lower face 18 is generallyplanar and horizontal so that it is generally parallel to the upper face16. However, other lower faces can be used, including a lower face thatincludes one or more concave portions or one or more channels overportions of the lower face 18. The distance d₆ between the upper face 16and the lower face 18 is preferably about 4.0 inches.

In the preferred block 10, the side faces 20, 22 are generally verticaland join the upper and lower faces 16, 18 and join the front and rearfaces 12, 14, as seen in FIGS. 1-3. At least a portion of each side face20, 22 converges toward the opposite side face as the side faces extendtoward the rear face 14. Preferably the entire length of each side face20, 22 converges starting from adjacent the front face 18, with the sidefaces 20, 22 being generally planar between the front and rear faces 12,14. However, it is possible that the side faces 20, 22 could startconverging from a location spaced from the front face 12, in which casethe side faces 20, 22 would comprise a combination of straight,non-converging sections extending from the front face and convergingsections leading from the straight sections to the rear face 14. Theconverging portion of each side face 20,22 preferably converges at anangle β of about 14.5 degrees.

Alternatively, the block 10 can be provided with only one convergingside face or side face portion, with the other side face beingsubstantially perpendicular to the front and rear faces 12, 14. A blockwith at least one converging side face permits serpentine retainingwalls to be constructed.

The block 10 also preferably includes a flange 26 that extends below thelower face 18 of the block, as seen in FIGS. 1-3. The flange 26 isdesigned to abut against the rear face of a block in the course belowthe block 10 to provide a pre-determined set-back from the course belowand provide course-to-course shear strength.

With reference to FIG. 3A, it is seen that the flange 26 includes afront surface 28 that engages the rear face of the block(s) in thecourse below. The flange 26 also includes a bottom surface 30, a front,bottom edge 32 between the front surface 28 and the bottom surface 30that is arcuate, and a rear surface 34 that is extension of, and forms aportion of, the rear face 14 of the block. The front surface 28 ispreferably angled at an angle γ of about 18 degrees. The angled frontsurface 28 and the arcuate edge 32 result from corresponding shapedportions of the mold, which construction facilitates filling of the moldwith dry cast concrete and release of the flange 26 from the mold.

As shown in FIGS. 1 and 2, the flange 26 extends the entire distancebetween the side faces 20, 22. However, the flange need not extend theentire distance. For example, the flange could extend only a portion ofthe distance between the side faces, and be spaced from the side faces.Alternatively, two or more flange portions separated from each other bya gap could be used.

With reference to FIG. 3A, the depth d₇ of the flange 26 is preferablyabout 0.750 inches. This depth defines the resulting set-back of theblock relative to the course below. Other flange dimensions could beused, depending upon the amount of desired set-back. The rear surface 34preferably has a height d₈ of about 0.375 inches.

The concepts described can also be applied to concrete blocks that areused in the construction of building walls, as well as to concretebricks, slabs and pavers. In these cases, it is contemplated and withinthe scope of the invention that neither side face of the block or brickwould converge, and that the flange would not be present. However, thepatterned front face would provide the block or brick a decorativeappearance.

Block Structures

The concrete block 10 of the present invention may be used to build anynumber of landscape structures. An example of a structure that may beconstructed with blocks according to the invention is illustrated inFIG. 4. As illustrated, a retaining wall 40 composed of individualcourses 42 a-c of blocks can be constructed. The blocks used inconstructing the wall 40 can comprise blocks having identicallypatterned front faces, or a mixture of blocks with different, butcompatibly-patterned faces. The height of the wall 40 will depend uponthe number of courses that are used. The construction of retaining wallsis well known in the art. A description of a suitable process forconstructing the wall 40 is disclosed in U.S. Pat. No. 5,827,015.

As discussed above, the flange 26 on the block 10 provides set-back ofthe block from the course below. As a result, the course 42 b isset-back from the course 42 a, and the course 42 c is set-back from thecourse 42 b. Further, as discussed above, the rearward incline of thefront face 12 reduces the ledge that is formed between each adjacentcourse, by reducing the amount of the upper face portion of each blockin the lower course that is visible between the front face of each blockin the lower course and the front face of each block in the adjacentupper course.

The retaining wall 40 illustrated in FIG. 4 is straight. However, thepreferred block 10 construction with the angled side faces 20, 22permits the construction of serpentine or curved retaining walls, suchas is disclosed in U.S. Pat. No. 5,827,015.

Block Forming Process

An additional aspect of the invention concerns the process for formingthe block 10. With reference to FIG. 5, an outline of the process isshown. Generally, the process is initiated by mixing the dry castconcrete that will form the block 10. Dry cast, no slump concrete iswell known in the art of retaining wall blocks. The concrete will bechosen so as to satisfy pre-determined strength, water absorption,density, shrinkage, and related criteria for the block so that the blockwill perform adequately for its intended use. A person having ordinaryskill in the art would be able to readily select a material constituencythat satisfies the desired block criteria. Further, the procedures andequipment for mixing the constituents of the dry cast concrete are wellknown in the art.

Once the concrete is mixed, it is transported to a hopper, which holdsthe concrete near the mold. As discussed below, the mold assembly 50includes at least one block-forming cavity 56 suitable for forming thepreferred block (see FIGS. 6-11). The cavity 56 is open at its top andbottom. When it is desired to form a block, a pallet is positionedbeneath the mold so as to close the bottom of the cavity 56. Theappropriate amount of dry cast concrete from the hopper is then loaded,via one or more feed drawers, into the block-forming cavity through theopen top of the cavity 56. The process and equipment for transportingdry cast concrete and loading a block-forming cavity are well known inthe art.

The dry cast concrete in the cavity 56 must next be compacted to densifyit. This is accomplished primarily through vibration of the dry castconcrete, in combination with the application of pressure exerted on themass of dry cast concrete from above. The vibration can be exerted byvibration of the pallet underlying the mold (table vibration), or byvibration of the mold box (mold vibration), or by a combination of bothactions. The pressure is exerted by a compression head, discussed below,that carries one or more stripper shoes that contact the mass of drycast concrete from above. The timing and sequencing of the vibration andcompression is variable, and depends upon the characteristics of the drycast concrete used and the desired results. The selection andapplication of the appropriate sequencing, timing, and types ofvibrational forces, is within the ordinary skill in the art. Generally,these forces contribute to fully filling the cavity 56, so that thereare not undesired voids in the finished block, and to densifying the drycast concrete so that the finished block will have the desired weight,density, and performance characteristics.

Pressure is exerted by a stripper shoe 94 that is brought down intocontact with the top of the dry cast concrete in the cavity 56 tocompact the concrete. The stripper shoe 94 acts with the vibration tocompact the concrete within the cavity 56 to form a solid, contiguous,pre-cured block. In the preferred embodiment, the stripper shoe alsoincludes a three-dimensional pattern 96 on its face for producing acorresponding pattern on the resulting pre-cured block as the strippershoe compacts the concrete. Preferably, the portion of the pre-curedblock contacted by the patterned shoe face comprises the front face ofthe block.

After densification, the pre-cured block is discharged from the cavity.Preferably, discharge occurs by lowering the pallet 82 relative to themold assembly, while further lowering the stripper shoe 94 through themold cavity to assist in stripping the pre-cured block from the cavity.The stripper shoe is then raised upwardly out of the mold cavity and themold is ready to repeat this production cycle.

If the block is to have one or more converging side walls, thencorresponding mold side walls, as described in detail below, must beprovided in the mold. Such mold side walls must be adapted to move intoa first position to permit filling of the mold, and compaction anddensification of the dry cast concrete, and must be adapted to move intoa second position to permit stripping of the mold without damage to thepre-cured block.

Once the pre-cured block has been completely removed from the cavity, itcan be transported away from the mold assembly for subsequent curing.The block may be cured through any means known to those of skill in theart. Examples of curing processes that are suitable for practicing theinvention include air curing, autoclaving, and steam curing. Any ofthese processes for curing the block may be implemented by those ofskill in the art.

Once cured, the blocks can be packaged for storage and subsequentshipment to a jobsite, and can then be used with other cured blocks informing a structure, such as the retaining wall 40 in FIG. 4.

Mold Assembly

The mold assembly 50 according to the present invention that is used topractice the invention is illustrated in FIGS. 6-11. The mold assembly50 is made from materials that are able to withstand the pressure thatis applied during formation of the pre-cured block, as well as providesufficient wear life.

The mold assembly 50 is constructed so that the pre-cured block isformed with its front face facing upward, and with its rear facesupported on the pallet 82 positioned underneath the mold assembly 50.This permits pattern impressing or other direct processing to occur onthe front face 12 of the block, to allow the formation of pre-determinedblock front faces. Pre-determined front faces can include front faceshaving pre-determined patterns and textures, front faces havingpre-determined shapes, front faces made from different material(s) thanthe remainder of the block, and combinations thereof.

Further, the mold assembly 50 is designed so that a pre-cured block,including a block with a lower lip or flange and/or one or moreconverging side faces, can be discharged through the bottom of the moldassembly.

Referring to FIG. 6, the mold assembly 50 comprises a mold 52 and acompression head assembly 54 that interacts with the mold 52 asdescribed below. The mold 52 comprises at least one block-forming cavity56 defined therein. In one preferred embodiment, the mold 52 is sizedfor use in a standard, “three-at-a-time” American block machine, havinga standard pallet size of approximately 18.5 inches by 26.0 inches,which is sized for making three blocks with their upper faces on thepallet. The mold 52 comprises a plurality of generally identicalblock-forming cavities 56. FIG. 7 illustrates five block-formingcavities 56 arranged side-by-side, which is possible when making thepreferred size blocks on a standard “three-at-a-time” pallet. Of course,larger machines that use larger pallets are in use, and this technologycan be used in both larger and smaller machines. The number of possiblemold cavities in a single mold depends upon size and/or type of themachine and the size of the pallet. A plurality of block-formingcavities 56 allows increased production of blocks from the single mold52.

With reference to FIG. 7, the cavities 56 are formed by division plates58, including a pair of outside division plates, a plurality of insidedivision plates, and a pair of end liners 60 that are common to eachcavity 56. The use of outside and inside division plates and end linersto form a block-forming cavity in a mold is known to those of skill inthe art. The division plates and end liners form the boundaries of theblock cavities and provide the surfaces that are in contact with thepre-cured blocks during block formation, and are thus susceptible towear. Thus, the division plates and end liners are typically mounted forremoval within the mold 52 so that they can be replaced as they wear orif they become damaged. The techniques for mounting division plates andend liners in a mold to form block cavities, and to permit removal ofthe division plates and end liners, are known to those of skill in theart.

In the preferred embodiment, the division plates 58 form the upper andlower faces 16, 18 of the blocks 10, while the end liners 60 form theside faces 20, 22. For convenience, the division plates and end linerswill hereinafter (including in the claims) be referred to collectivelyas the side walls of the cavities. Thus, side walls refers to divisionplates and end liners, as well as to any other similar structure that isused to define the boundaries of a block-forming cavity.

Referring now to FIG. 8, a portion of a single block-forming cavity 56is illustrated. The cavity 56 defined by the side walls 58, 60 has anopen top 64 and an open bottom 66. As shown, the top ends of the sidewalls 60 (e.g. the end liners) are connected by pivots 62 to suitablesurrounding structure of the mold 52 to allow the side walls 60 to pivotbetween the closed position shown in FIG. 8, where the side walls 60converge toward each other, to a retracted position where the side walls60 are generally vertical and parallel to each other (not shown). In theretracted position, the bottom of the cavity 66 is at least as wide asthe top of the mold cavity, which allows the pre-cured block to bedischarged through the open bottom. When only a portion of either sideface 20, 22 of the block converges, only a corresponding portion of theside walls 60 will be pivoted. The side wall 58 that forms the lowerface of the block 10 is also illustrated in FIG. 8, while the other sidewall 58 that forms the upper face of the block is not shown.

Pivoting of the side walls 60 is required in order to form the preferredblock 10. As discussed above, the block 10 is formed “face-up” in themold 52 with its converging side faces formed by the side walls 60.Thus, the converging side walls 60, when they are angled as illustratedin FIG. 8, shape the converging side faces 20, 22 of the pre-curedblock. However, the front portion of the pre-cured block is wider thanthe rear portion of the block. In order to be able to discharge thepre-cured block through the open bottom 66, the side walls 60 must pivotoutward to enable downward movement of the pre-cured block through theopen bottom.

Biasing mechanisms 68 are provided to maintain the side walls 60 at theconverging position during introduction of the concrete and subsequentcompacting of the dry cast concrete, and which allow the side walls 60to pivot to a vertical position during discharge of the pre-cured block.Preferably, a single biasing mechanism 68 is connected to each side wall60 that is common to all cavities 56, so that the movement of each sidewall 60 is controlled via a common mechanism (see FIG. 7).Alternatively, separate biasing mechanisms can be provided for eachcavity. The biasing mechanisms 68 are illustrated as comprising airbags, which will be controlled through the use of air or similar gas.Suitable inlet and outlet ports for the air will be provided, as will asource of high pressure air. The use of biasing mechanisms other thanair bags is also possible. For example, hydraulic or pneumatic cylinderscould be used.

When pressurized with air, the air bags will force the side walls 60 tothe position shown in FIG. 8. When it comes time to discharge thepre-cured block(s), the pressurized air is vented from the air bags,which allows the side walls 60 to pivot outward under force of thepre-cured block as the pre-cured block is discharged through the openbottom when the pallet is lowered. During block discharge, the sidewalls 60 remain in contact with the side faces of the pre-cured block.Alternatively, biasing mechanisms, such as coil springs, can beconnected to the side walls 60 to force the side walls to the retractedposition when the air bags are vented. In this case, as the pallet 82starts to lower to begin block discharging, the side walls 60 will beforced to the retracted position, and the side walls 60 will not contactthe side faces of the block during discharge. After discharge, the sidewalls 60 are returned to the closed, angled position by re-pressurizingthe air bags.

Rather than pivoting the side walls 60, it is possible to use othermechanisms to permit movement of the side walls 60 to allow discharge ofthe pre-cured block. For example, the side walls 60 could be mounted soas to slide inwards to the position shown in FIG. 8 and outwards to aposition where the bottom of the cavity 56 is at least as wide as thetop of the mold cavity. The sliding movements could be implemented usinga track system in which the side walls are mounted.

As shown in FIG. 8, each side wall 60 includes a shaping surface 76 thatfaces the cavity 56. The shaping surfaces 76 are substantially planar.The result is the formation of substantially planar side faces 20, 22 ofthe block 10.

Referring now to FIG. 9, the side walls 58 that form the upper and lowerfaces 16, 18 of the block 10 are illustrated. The side walls 58, whichare fixed and not moveable during the molding process, are substantiallyvertical.

The side wall 58 that forms the upper face 16 (the left side wall 58 inFIG. 9) includes a shaping surface 78 that faces the cavity 56. Thesurface 78 is substantially planar, which results in the formation of asubstantially planar upper face 16.

The side wall 58 that forms the lower face 18 (the right side wall 58 inFIG. 9) includes an undercut, or “instep,” portion 80 at the bottom edgethereof adjacent the open bottom 66. The undercut portion 80, incombination with the pallet 82 that is introduced under the mold 52 totemporarily close the open mold bottom 66 during the molding process,defines a flange-forming subcavity of the cavity 56. The flange-formingsubcavity has a shape that results in the formation of the flange 26 onthe block 10.

In particular, the undercut portion 80 includes a shaping surface 84that forms the front surface 28 of the flange 26, a shaping surface 86that forms the bottom surface 30 of the flange, and a shaping surface 88that forms the edge 32 of the flange 26. The portion of the flange 26that is an extension of the rear face 14 is formed by and on the pallet82, along with the remainder of the rear face 14. The shape of thesurfaces 84 and 86 facilitate filling of the undercut portion 80 withthe concrete during introduction and subsequent compacting of theconcrete so that the flange 26 is completely formed, as well as aid inrelease of the flange 26 from the surfaces 84, 86 during blockdischarge.

In the case of a block having a flange on the lower face and noconverging side faces, the side walls 60 would be oriented verticallyinstead of being converging. Further, in the case of a block without aflange on the lower face and with converging side faces, the undercut 80would not be present. In the case of a block without a flange on thelower face and without converging side faces, the undercut 80 would notbe present and the side walls 60 would be oriented vertically.

Returning to FIGS. 6 and 8, the head assembly 54 is seen to include acompression head 90 in the form of a plate. The head 90 is actuated byan actuating mechanism in a manner known in the art so that the head 90is moveable vertically up and down to bring about compaction of the drycast concrete in the mold cavities 56 and to assist in stripping thepre-cured blocks from the mold 52.

Connected to and extending from the bottom of the head 90 is a pluralityof stand-offs 92, one stand-off for each block-forming cavity 56 asshown in FIG. 6. The stand-offs 92 are spaced from each other, with thelongitudinal axis of each stand-off oriented perpendicular to the planeof the head 90 and extending generally centrally through theblock-forming cavity 56.

Stripper Shoe

A stripper shoe 94, illustrated in FIGS. 6, 8, 9 and 11, is connected tothe end of each stand-off 92. The stripper shoe 94 is rectangular inshape and is dimensioned so that it may enter the respective cavity 56through the open top to contact the concrete to compact the concrete,and to travel through the cavity during discharge of the pre-curedblock. The dimensions of the stripper shoe 94 are only slightly lessthan the dimensions of the open top 64 of the cavity 56, so that theshoe 94 fits into the cavity 56 with little or no spacing between thesides of the shoe 94 and the side walls 58, 60 defining the cavity. Thisminimizes escape of concrete between the sides of the shoe 94 and theside walls 58, 60 during compression, and maximizes the front face areaof the block that is contacted by the shoe 94.

Flanges 98 a, 98 b are formed on opposite ends of the face of thestripper shoe 94, as best seen in FIG. 11. The flanges 98 a, 98 b arearcuate to produce the rounded edges 24 a, 24 b on front face 12 of theblock. If desired, arcuate flanges can be provided on the two remainingends of the stripper shoe 94, in order to produce upper and lowerrounded edges on the front face 12.

As discussed above, a face of the shoe 94 is preferably provided with apre-determined pattern 96 that is a reverse image of a desired surfaceor surfaces. As the shoe 94 including the pattern 96 compacts theconcrete, the pattern is imparted to the front face of the block. Thepattern 96 preferably simulates natural stone, so that the front face ofthe resulting block simulates natural stone thereby making the blockappear more natural and “rock-like.” A variety of different patterns 96can be provided on the shoe 94, depending upon the appearance of thefront face that one wishes to achieve. In addition to, or separate from,the pattern 96, the face of the shoe 94 can be shaped to achieve afaceted or curved block front face. Indeed, the face of the shoe 94 canbe patterned and/or shaped in any manner which one desires in order toachieve a desired appearance of the block front face.

FIGS. 10A-F and 11 provide examples of patterns 96 that can be providedon the shoe 94. The patterns 96 simulate naturally occurring objects,such as, for example, natural stone or man made objects. The pattern 96is preferably machined into the shoe face based upon a pre-determinedthree-dimensional pattern. An exemplary process for creating thepre-determined pattern 96 on the shoe face follows.

Referring now generally to FIG. 12, initially, one or more objects areselected. For example, the objects may include one or more natural rockshaving surfaces which one considers to be visually pleasing. Othernatural or man made objects may also be used.

One or more of the rock surfaces are then scanned using a digitalscanning machine. An example of a suitable scanning machine forpracticing the invention is the Laser Design Surveyor® 1200 having anRPS 150 head, available from Laser Design Incorporated of Minneapolis,Minn. The Laser Design Surveyor® 1200 has a linear accuracy of 0.0005inch in the XYZ coordinates, and a resolution of 0.0001 inch. Aspracticed, data is collected at 256 points for every 0.004 inch of theone or more rock surfaces being scanned. The rock surfaces may bescanned at as many angles as necessary to collect data on all surfaces.

Once the scanned data has been collected, various techniques can be usedto manipulate the data. Initially, the Laser Design Surveyor® utilizesDataSculpt® software, available from Laser Design, Inc. of Minneapolis,Minn., to generate one or more DataSculpt® point clouds, or data setsincluding data points positioned in X, Y, and Z coordinates, from thescanned data.

A computer-aided design (CAD) package is then used to trim the pointclouds. The point clouds are also sampled to reduce the scanned data toa manageable size, while smoothing the data by removing extraneouspoints and noise. Next, the data from the point clouds are blended toform a finished point cloud. The finished point cloud is converted to apolygonal mesh, or a three-dimensional rendition of the point cloudusing polygonal shapes. The edges of the polygonal mesh are trimmed toform a clean line, and boundaries are applied to form a tight meshpattern. Using the mesh, grids are applied and converted to aNon-Uniform Rational B-Splines (NURBS) surface.

The resulting digital image is displayed (see, e.g., FIGS. 10A-F). Theuser can manipulate the digital image by selecting and modifying one ormore points on the digital image in the X, Y, and/or Z directions. Next,the data is scaled and/or trimmed to an overall block dimension, in theillustrated embodiment 3.88 inches by 11.88 inches per print. Inaddition, the data is modified to meet a ¾ inch maximum difference inface relief, a 0-10 degree face angle from the lower edge of the face tothe upper edge of the face, and a 5-10 degree draft for all interiorsurfaces of the relief. Next, the complete data file is mirrored tocreate the reverse image needed to create the stripper shoe 94. The datacan be output in an Initial Graphics Exchange Specification (IGES)format to a CAD system described below.

A CAD system suitable for manipulating the scanned data is theMastercam® Mill Version 8.1.1, available from CNC Software, Inc. ofTolland, Conn.

The data, in IGES format, is then input into preferably a three axis (orfour axis), numerically controlled milling machine for milling of thestripper shoe 94. The data is converted into toolpaths by the millingmachine. Using the toolpaths, the milling machine mills a mirror imageof the rock surface into the face of the stripper shoe 94.

To create the illustrated stripper shoes, the milling machine canperform a series of toolpaths, including: (1) a first toolpath with a ½inch diameter flat bottom endmill doing a parallel pocket at 90 inchesper minute (IPM) and 7,000 revolutions per minute (RPM); (2) a secondtoolpath with a ¼ inch diameter flat bottom endmill doing a surfacecontour at 100 IPM and 10,000 RPM; (3) a third toolpath with a ¼ inchdiameter ball endmill doing a 45° surface contour at 100 IPM and 12,000RPM; and (4) a fourth toolpath with a ⅛ inch diameter ball endmill doinga 45° surface contour at 150 IPM and 14,000 RPM. The number and type oftoolpaths may vary based on the complexity of the surface beingreproduced.

A suitable milling machine for practicing the invention is the MikronVCP600 available from Mikron AG Nidau of Nidau, Switzerland.

The result is a pattern milled into the face of the shoe 94 that is amirror image of the desired pattern of a block. When the shoe 94including the pattern compacts the concrete used to form the block, thepattern is impressed into the front face of the block. In theillustrated embodiments shown in FIGS. 10A-F and 11, the resultingthree-dimensional pattern has a relief of between about 0.5 inch andabout 1.0 inch, preferably no greater than about ¾ inch.

This process can be repeated to produce additional shoes having the sameor different face patterns. This is advantageous because the patternedface of each shoe is subject to wear, and the shoe will need to bereplaced when the pattern becomes excessively worn. Moreover, multipleshoes can be used for multiple molds. Further, by forming a variety ofdifferent pre-determined shoe patterns, a variety of different blockfront face appearances can be achieved. Other shoe patterns can beformed by combining the scanned surfaces of a plurality of differentrocks. Exemplary shoe patterns are illustrated in FIGS. 10A-F and 11.

As discussed above, the resulting detail and relief that is provided onthe block front face can be significantly greater than the detail andrelief that is provided on the front face of a block that results fromconventional splitting techniques, and the other front face distressingtechniques discussed above. If desired, the scan data can be manipulatedin order to increase or decrease the relief that is milled into the shoeface, which will alter the relief that is ultimately provided on theblock front face.

It is known in the art that dry cast concrete may have a tendency tostick to mold surfaces, such as the patterned surface of the strippershoe 94. Various techniques to enhance the release of the stripper shoe94 from the dry cast concrete are known, and one or more of them mayneed to be employed in the practice of this invention. For example, thepattern formed on the stripper shoe has to be designed to enhance,rather than inhibit, release. In this regard, appropriate draft angleshave to be employed in the pattern. As noted above, in the illustratedembodiment, a draft angle of 5° is used. The pattern-forming techniquesdescribed above permit manipulation of the scanned images to createappropriate draft angles. Release agents, such as a fine mist of oil,can be sprayed onto the stripper shoe between machine cycles. Headvibration can be employed to enhance release. And heat can be applied tothe stripper shoe to enhance release. Heating mold components to preventsticking of dry cast concrete is known in the art. In the presentinvention, due to the detailed pattern that is to be imparted to theblock front face, it is even more important to prevent sticking. Inparticular, it is important to be able to control the temperature of theshoe so that the temperature can be maintained at selected levels.

Preferably, as shown diagrammatically in FIG. 13, a heater 100 isconnected to the shoe 94 for heating the shoe. The heater 100 iscontrolled by a temperature control unit 102. A thermocouple 104 mountedon the shoe 94 senses the temperature of the shoe, and relays thatinformation to a power control unit 106 that provides electrical powerto the control unit 102 and the heater 100. The system is designed suchthat, when the temperature of the shoe 94 falls below a pre-determinedlevel as sensed by the thermocouple 104, power is provided to the heater100 to increase the shoe temperature. When the shoe temperature reachesa pre-determined level, as sensed by the thermocouple, the heater 100 isshut off. Thus, the shoe temperature can be maintained at selectedlevels. Preferably, the control unit 102 is designed to allow selectionof the minimum and maximum temperature levels, based on the dry castconcrete that is being used. In the preferred embodiment, the surfacetemperature of the stripper shoe 94 is maintained between 120° F. and130° F.

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

What is claimed is:
 1. A process for producing a concrete block havingupper and lower faces, a front face, a rear face, and opposed sidefaces, the method comprising the steps of: providing a mold having aplurality of side walls defining a mold cavity with an open top and anopen bottom; positioning a pallet having a flat surface underneath themold to temporarily close the entire open bottom of the mold cavity withthe flat surface of the pallet; introducing dry cast concrete into themold cavity through the open mold top; compacting the dry cast concreteto form a pre-cured concrete block with the rear face of the blockresting on the pallet and the front face of the block facing upward, thecompacting including introducing a stripper shoe having a face thatcomprises a mirror image of a three-dimensional pattern that simulatesnatural stone into the mold cavity through the open top of the moldcavity, the three-dimensional pattern having a maximum relief of atleast about 0.5 inch; pressing the patterned face of the stripper shoeagainst the dry cast concrete contained in the mold cavity, to impart apattern that simulates natural stone to the front face of the pre-curedconcrete block with a maximum relief of at least about 0.5 inch;reopening the temporarily-closed bottom of the mold cavity; dischargingthe pre-cured concrete block from the mold cavity through the reopenedbottom of the mold cavity; and curing the pre-cured concrete block. 2.The process of claim 1, wherein the compacting step includes vibratingthe concrete contained in the mold cavity.
 3. The process of claim 1,wherein the step of discharging the pre-cured concrete block through theopen bottom of the mold cavity includes lowering the pallet relative tothe mold.
 4. The process of claim 1 wherein said mold includes aplurality of said mold cavities which operate with a single flat pallethaving an entirely flat mold-receiving surface to mold a plurality ofblocks at the same time.
 5. The process of claim 1 wherein the step ofcompacting includes using a stripper shoe having a face with the mirrorimage of a three-dimensional pattern that simulates natural stoneresulting from digital scanning of a selected three-dimensional patternto create scanned data in XYZ coordinates and using the data to createthe face of the stripper shoe.
 6. The process of claim 1 wherein thestep of pressing the patterned face of the stripper shoe against the drycast concrete contained in the mold cavity, to impart a pattern thatsimulates natural stone to the front face of the pre-cured concreteblock includes imparting the three-dimensional pattern to have a maximumrelief of at least about 1.0 inch.
 7. The process of claim 1 wherein thestep of pressing the patterned face of the stripper shoe against the drycast concrete contained in the mold cavity to impart a pattern thatsimulates natural stone includes imparting a pattern that simulates asingle stone.
 8. The process of claim 1 wherein the step of pressing thepatterned face of the stripper shoe against the dry cast concretecontained in the mold cavity to impart a pattern that simulates naturalstone includes imparting a pattern that simulates multiple stones in amortared together pattern.
 9. The process of claim 1 wherein the step ofpressing the patterned face of the stripper shoe against the dry castconcrete contained in the mold cavity to impart a pattern that simulatesnatural stone includes imparting a pattern that simulates multiplepieces of stone stacked in layers.